372 EwAKT — Variation : Germinal and Environmental. 



equally represented. Had the germ-cells in the case of the pigeons succeeded in 

 developing apart, they would have given rise to tv^ins, one black like the male 

 parent, the other the image of the white female parent. 



2. The offspring may resemble one of the parents. This is frequently the 

 case when wild members of a species are crossed with tame varieties of the same 

 species, e.g. when wild and tame rabbits, rats, and mice are intercrossed. The 

 same result is sometimes obtained by crossing members of two distinct genera. 

 When the orchid Zygopetalum Mackayi is crossed with certain species of Odonto- 

 glossum {e.g. Pescatorei and crisjmm), the hybrids are " Zggoj^etalum Uackagi,''^ 

 pure and simple, without any trace of the peculiar structure of the pollen parent 

 in any case.* 



Very often one tame variety is prepotent over another. I have a yellow and 

 white (skewbald) pony that two years ago produced to a bay pony a foal, which in 

 its colour, disposition, and gait is the image of her dam. When quite young, this 

 pony produced to a sire, more pi-epotent than herself, a dark dun-coloured foal. 

 That Gralloway are prepotent over Highland cattle has already been mentioned. 

 In the same way, a silver-grey rabbit proved prejDotent over a Himalaya doe — of 

 thirty-nine young, all resembled in colour, though not in make, the silver gi'ey 

 buck. So in pigeons, one breed of a given colour may prevail. A "restored" 

 rock pigeon proved on one occasion prepotent over a barb, and a white fan, the 

 offspring of two blue fans, produced a perfectly white bird when mated with his 

 own dam. 



We often account for the pi'epotency of one genus, species, variety, or race, by 

 saying it belongs to an older type. This explanation, however, is sometimes at 

 fault, for quite a new type may be prepotent over an old one. Some time ago 

 I saw in Kent a "calico" or "painted" mule spotted all over like an Indian 

 " painted " (pinta) pony. As a rule mules are more like the ass sire than the horse 

 dam, but when the dam is a "sport" some of the hybrid offspring may fairly 

 accurately reproduce her recently acquired peculiarities, such as spots or large 

 blotches. Again, a dark variety of the peppered moth has recently largely 

 disjjlaced the older and lighter variety over a considerable part of England. 



In these cases the result evidently depends on the germ-plasm of one of the 

 parents being overpowering, able to dominate the germ-plasm provided by the 

 other parent — on the germ-plasms being antagonistic or at least incapable of 

 blending. 



Hence it follows that in some cases the prepotency may be regarded as 

 quite indeijendent of the environment, in e.g. the wild rabbit, rat, and mouse, 

 while, in others, it may, to a considerable extent, depend on the maturity of 

 the germ- cells. 



*Hm-st, Nature, Dec. 22, 1898. 



